1. Technical Field
Containers that can be reused and that are suitable for the manufacturing, production, storage and transportation of cheese products.
2. Background
In this specification where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date, publicly available, known to the public, part of common general knowledge, or otherwise constitutes prior art under the applicable statutory provisions; or is known to be relevant to an attempt to solve any problem with which this specification is concerned.
Cheese is made within block-shaped containers that are also used to ship or otherwise transport and store the cheese for further processing. Some of the containers are made of stainless steel with permanently joined sides, others are made with plywood sides that are temporarily held together between metal components by banding or stretch wrap, while still others are made of plastic resin material and held together with interlocking corners without the need for horizontal banding or stretch wrap. These containers have approximately 18,000 cubic inches (i.e., 295 liters) of capacity for making blocks of cheese weighing about 700 pounds (or about 315 kilograms).
The sides of the containers are assembled together to constitute a so-called “cheese hoop,” which is used independent of a pallet or base and cover (also referred to as a “lid”) of the containers during the cheese-making process. In the direct-fill process, the cheese is pressed from both ends of the hoop, sometimes in the presence of a vacuum, to remove whey and air from the coagulated part of the cheese, knitting cheese curds into a cohesive block. The compression of the cheese exerts large outward pressures against the cheese hoops, and the sides and joints between the sides of the cheese hoops must be especially strong to resist these pressures.
Finished cheese is extruded in large blocks from the stainless steel containers for further processing, whereas the sides of the plywood containers and plastic containers can be taken apart to remove the blocks of cheese. Once removed from the containers, the blocks of cheese are further processed by forcing the blocks through a matrix of wire cutters for cutting the blocks into a number of smaller blocks which are often of exact weights for consumer sizes. Any variation from the block's targeted dimensions, squareness and flatness, such as bowing or denting, produces waste that is trimmed from the exterior of the blocks. Trim scrap is repurposed for use in making processed cheese or shredded cheese, adding to handling costs and often reducing the market value of the cheese and overall profitability.
Accordingly, the cheese containers must be made to exacting tolerances and be especially rigid. In fact, the containers are generally required to hold dimensions of the finished cheese blocks to within ⅛th of an inch (or approximately 3 millimeters). However, the stainless steel containers tend to become dented with repeated use and produce increasing amounts of scrap. The dents also make extruding the blocks of cheese from the stainless steel containers more difficult. Stainless steel cheese containers have the additional disadvantages of high initial cost; high weight, increasing freight costs; and the inability to be dissembled for cost-effective return shipping of empties. For these reasons, the use of stainless steel cheese containers is limited to a small number of in-plant operations.
The plywood and metal containers have a much lower initial cost than the stainless steel containers and resist denting; but the plywood poses sanitation problems associated with the wood porosity and splinters, as well as rust and paint from the painted carbon steel frames. Plywood containers are also difficult to assemble due the large number of components (8 to 12 components per container) and the need for horizontal banding or stretch wrap to hold hoops together. The plywood is stripped and re-waxed between uses for sanitary reasons, while metal components are stripped of wax and paint, repaired, repainted and rewaxed before the containers can be used again to make cheese. This is both a costly process and a process with substantial negative impact on the environment in terms of solid waste and energy consumption, as well as greenhouse gas and other emissions.
Plastic cheese containers, such as those described in U.S. Pat. No. 5,287,981, have substantial advantages over stainless steel and plywood containers. For example, plastic cheese containers, made of food grade materials, can easily be washed between uses in a process that is less costly, less energy intensive and reduces solid waste, greenhouse gas and other emissions relative to the wood and metal container reconditioning process. Plastic cheese containers are also easier to assemble, with fewer components (6 components per container) and eliminate the need for horizontal banding or stretch wrap to hold the hoops together, further reducing cost and solid waste. Plastic cheese containers are much lighter than plywood containers (about 95 lbs. for plastic vs. 110 to 120 lbs. for plywood), reducing freights costs by permitting 1 or 2 more containers full of cheese to be shipped on over-the-road trailers, from 54 plywood containers full of cheese per trailer to up to 56 plastic containers per trailer, without exceeding weight limits. This weight reduction further reduces return freight costs by allowing more empty, disassembled containers to be shipped per trailer loads—from about 360 to 400 for wood to about 450 to 475 for plastic containers.
Plastic cheese containers, as described in U.S. Pat. No. 5,287,981, have grown in market share since introduction. However, they have certain attributes that can be improved upon to further benefit the market. These improvements are the subject of this invention. Existing plastic cheese containers interlock in corners using male interlock elements referred to as tenons, lugs, fingers or hooks protruding off the end faces of one set of opposing walls, and a second set of opposing walls providing female interlocking elements referred to as mortises or hook receivers. Male interlocking tenons or hooks extend into female interlocking mortises or hook receivers, then adjacent walls move in opposite directions along the vertical axis to lock in place, forming an interlock that restricts rotation around the vertical axis of each corner (a non-rotational interlock). Corners are locked and held in place as a result of friction and interferences between the tenons or hooks and mortises or hook receivers. These joints have the added feature of all locking elements remaining within the plane of the inner and outer surfaces of each pair of adjoining walls. This style of joint, while effectively resisting rotation around the vertical axis of each corner to help minimize deflection in the walls and maintain cheese block flatness, results in high stresses in the joint. The friction or interference fit does not provide a positive lock. The friction/interference fit also necessitates the use of tooling to assemble and disassemble the interlocks.
Another element common in the current state of the art of plastic cheese containers is that narrower endwalls have substantially greater resistance to deflection than wider sidewalls. This discrepancy in stiffness has the unintended consequence of rotating fixed corners toward the endwalls and away from the sidewalls, further increasing deflection of sidewalls.
All cheese containers incorporate an additional set of components referred to as a pressboard and springs (referred to by some as a “spring plate”). Pressboards are placed on top of the block of cheese after it is formed, but before the cover is attached. Springs of varying configuration are then placed on the pressboard and the cover is placed on the springs. Cheese containers are closed by pressing down on the cover to compress springs against the pressboard and then banded in place. This spring and pressboard assembly maintains pressure on the cheese and travels down into the hoop to take up space vacated by further loss of whey and closing of air gaps as the cheese is cooled, and aged during storage and shipment. This improves the homogeneity and quality of the cheese. In existing cheese containers the pressboard and springs reduce the volume available in the container by at least the thickness of the pressboard and the fully compressed springs, often by over ½ inches.
All cheese containers include a pallet or base, in addition to the 4-sided hoop, pressboard, springs and a cover for fork truck and pallet jack handling and stacking. Pallets of existing plastic cheese containers have legs, feet or runners that are formed from the bottom using various forms of the injection molding process. That common design allows pallets to be formed in one piece with a solid top surface to support the cheese and no secondary assembly, closed cavities or seams that can increase manufacturing costs and make pallets more difficult to clean. That design includes ribs forming the sides of the feet sitting on the floor. Said ribs can develop burrs when pallets are slid on the floor, catch on imperfections in the floor, wear down with use, and sustain damage. That design presents the further problem of increased pallet weight due to the need for the walls of the feet to be tapered for removal from the mold resulting in very thick sections at the top of the feet in order to achieve adequate thickness at the bottom of the feet to resist damage.